Ukraine's opposition have called off a massive rally because of the funeral for a protester killed in clashes with police last week.

Mikhail Zhiznevsky, 25, was one of two protesters who died of gunshot wounds on Wednesday. The opposition contends they were shot by police in an area where demonstrators had been throwing rocks and firebombs at riot police for several days.

The memorial service is to take place at Independence Square in the centre of Kiev, where protesters have established a large tent camp and held demonstrations around the clock since early December. Sunday rallies in previous weeks have attracted especially large crowds, sometimes exceeding 100,000 people.

The protests began in late November after President Viktor Yanukovych shelved a long-awaited agreement to deepen ties with the European Union, but they have been increasingly gripped by people seeking more radical action even as moderate opposition leaders have pleaded for a stop to violence.

A crowd besieged a building on Saturday throwing fireworks, firebombs and rocks, near the protest tent camp where about 200 police were sheltering, but had created a corridor allowing police to leave by Sunday.

Thousands of people were already in the square on Sunday afternoon, but opposition leaders may be betting that by not formally calling people together for a rally the event will be smaller.

The overnight outburst came soon after opposition leaders issued a defiant response to Yanukovych's offer to make Arseniy Yatsenyuk, one of their top figures, the country's prime minister. While not rejecting the offer outright, Yatsenyuk said more of the opposition's demands must be met, including Yanukovych's resignation. He vowed protests will continue.

About half of Ukraine's people favoured deeper integration with the EU, according to polls, and many Ukrainians widely resent Russia's long influence over the country.

In the past week, demonstrators have seized government administration buildings in a score of cities in western Ukraine, where Yanukovych's support is weak and desire for European ties is strong.